Myo-inositol (MI) plays an important role in a variety of plant cellular processes with potentially significant agronomic impact. For example, MI is a precursor in the formation of the cell wall components hemicellulose and pectin, which affect plant processing properties and nutritional content. See, e.g., U.S. Pat. No. 6,194,638; U.S. Patent Application No. 20030079251; and Loewus and Murthy (2000) Plant Sci. 150:1-19, all of which are herein incorporated by reference. MI is also involved in the synthetic pathway leading to the production of phytic acid salts (phytates), which both reduce the nutritive content of feed and, in animal waste, are a major source of surface and ground water pollution. See, e.g., U.S. Pat. Nos. 6,197,561 and 6,291,224; and U.S. Patent Application No. 20030079247, all of which are herein incorporated by reference.
Catabolism of MI occurs via a single pathway, the MI oxidation pathway (see Loewus and Murthy (2000) Plant Sci. 150:1-19). The first committed step in this pathway is the conversion of MI to D-glucuronic acid (glucuronate) by the enzyme myo-inositol oxygenase (MIOX; synonymously meso-inositol oxygenase, myo-inositol:oxygen oxidoreductase, or EC 1.13.99.1). The MIOX protein has been isolated from a variety of organisms, including oat seedlings (Koller et al. (1976) Mol. Cell. Biochem. 10:33-39), and the corresponding gene sequence has been determined for, e.g., rats, mice, humans, and pigs. See Arner et al. (2001) Biochem. J. 360:313-320, herein incorporated by reference.
In light of the involvement of MI in plant cellular processes, it would be advantageous to increase or decrease the amount of this compound in order to modulate these cellular processes, and thereby improve the agronomic properties of plants.